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Subject: Re: this is simply wrong

Author: Charles Worthington

Date: 18:55:31 02/19/03

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On February 19, 2003 at 21:46:55, Charles Worthington wrote:

>On February 19, 2003 at 21:27:28, Anthony Cozzie wrote:
>
>>On February 19, 2003 at 20:58:20, Charles Worthington wrote:
>>>That is like comparing a Yugo to a Ferrari.
>>
>>OK, as a computer architecht I have to correct this foolery.
>>
>>1. Deeper pipelining do not necessarily lead to greater performance.
>>   A deeper pipeline decreases the cycle time of the processor, but increases
>>the branch misprediction penalty and causes all sorts of other nasty forwarding
>>stalls.  Intel believes in superpipelining; I read a paper where they have
>>simulated a 50 stage pipeline and believe it has higher performance. There are
>>also people who think this is hogwash.
>>
>>2. It is very difficult to determine the cycle time of a circuit
>>   The problem is that the TOPOLOGICAL longest path is not always the longest
>>data correct path.  It is very difficult to give a good example for this, but I
>>suggest you do a search for 'false path' on google and read up a bit.  When
>>intel makes chips, they don't classify them as 2.8GHZ or 3.06GHZ.  They just
>>make chips.  When the test them according to heat resistance, etc, then they are
>>classified.  This is why overclocking a PIV 2.2GHZ to 3.0GHZ is safe;
>>overclocking a 3.0GHZ to 4.0GHZ is much more suspect: no one knows all the real
>>limits in the chip.  The chip may have very very annoying corner cases where it
>>fails.
>>
>>3. Processor performance is very dependent on the application.
>>   Anandtech did a review of the Barton version of the Athlon [512KB cache].  In
>>some benchmarks the PIV beat the Athlon, and in some the reverse.
>>Unreal 2003 Botmatch: AMD over PIV, 75:70
>>Rendering Time in in 3DMAX: PIV over AMD, 169:227.
>>
>>    This brings up another point.  Intel has a vision of the processor as the
>>multimedia center of the home.  The PIV is designed to excel at multimedia
>>signal processing applications (like 3DMAX).  These applications have few
>>branches and a great deal of parallelism; the deep pipeline of the PIV does not
>>matter.  A Chess Engine, however, is integer code with lots of branches, which
>>is why the Athlon usually performs well.
>anthony
>
>I wasnt speaking of performance i was speaking mainly of purpose. Do you feel
>that AMD honestly markets their product and condones the ridiculous overclocking
> figures that we see here? Perhaps I will write AMD and post their reply here.
>>charles

Although I do see your point on the performance issue. :-)



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